DNA-DNA hybridization studies assessing the relationships between kappas (intracellular bacteria of the protozoan Paramecium) from different part of the world are being carried out. Related intracellular bacteria are also being studied. The effects of toxins produced by the bacteria are being studied. Work on the size distribution and chromatin isolated from the macronucleus of Paramecium is under investigation. BIBLIOGRAPHIC REFERENCES: Preer, L.B. and J.R. Preer, Jr. 1977. Inheritance of infectious elements. In "Cell Biology: A Comprehesive Treatise," ed. L. Goldstein and D.M. Prescott, vol. 1, Chapt. 7. In press. Preer, Jr., J.R. 1977. The killer system in Paramecium--kappa and its viruses. In "Microbiology - 1976", ed. P. Lemke. In Press.